I2C and The Arduino Mega

Using Arduino Project Guidance
1

Hi all,
i have an example sketch for reading a CMPS10 compass using I2C from the wire library.
it states its using pins 4 & 5.
on the Mega i have 2 dedicated pins 20 and 21.
as far as i can tell the library is loaded on the AVR Ic already on the mega.
does that mean i can use the wire library and it will already be updated to run the mega on pins 20 and 21.
Cheers
J.

2

The wire library will support both standard and mega boards by just changing the wiring for clock and data pins, no other changes required.

Lefty

3

Thanks Lefty,
i couldnt see for looking for it.
J.

4

I have experimented with the CMPS10 Compass from active robots connected to the mega. but it still isnt responding.
has anyone got this device working with the mega 2560 board.
I have noticed on active robots site/example that there is 2x 1.8k ohm resistors between the SDA, SCL lines and the 5V rail.
is this still required on the mega (with its dedicated I2C communication connection-ie are pullup resistors already connected internally)
any help would be very much appreciated

5

2x 1.8k ohm resistors between the SDA, SCL lines and the 5V rail.
is this still required on the mega

Yes but I would use 4K7 for a 5V system, not 1K8.

6

Hi Mike,
Thanks for the advice. i will get a couple out of the workshop tommorow and try it again.

I was trying to give you some piece and tap someone else for help, but its good to hear from you.
Cheers
Jason